1. Field of the Invention
The invention relates generally to integrated circuits, and more particularly to systems and methods for reducing simultaneous switching noise within integrated circuits by providing decoupling capacitors that are positioned with higher concentrations near hot spots in the integrated circuits.
2. Related Art
As computer-related technologies have developed, technical advances have been matched by a demand for increased speed and processing capacity. This has resulted in the development of integrated circuits with larger and larger numbers of smaller and smaller circuit components. Integrated circuits commonly contain millions of transistors that form the various logic gates, latches, amplifiers and other components within the integrated circuits.
As the complexity of an integrated circuit increases, and the number of components in the integrated circuit grows, designers are often faced with problems that were either less acute in earlier, less complex circuits, or were not present at all in these circuits. For example, as the number of transistors in integrated circuits increases, the amount of simultaneous switching noise generated by the transistors typically increases as well. This switching noise can reduce the performance of the integrated circuits or even impede their proper functioning.
The problem of increased switching noise is conventionally addressed by connecting decoupling capacitors to the integrated circuit. The decoupling capacitors are typically positioned externally to the integrated circuit package, with one of the leads of each decoupling capacitor connected to the ground planes in the integrated circuit, and the other lead connected to the power planes in the integrated circuit.
Conventionally, the decoupling capacitors are positioned on the underside of the substrate on which the integrated circuit die is manufactured. This allows the decoupling capacitors to be located close to the integrated circuit die, while also allowing a heat sink or heat spreader to be placed in contact with the integrated circuit die. The decoupling capacitors are typically distributed evenly across the area on the underside of the integrated circuit die. Because the height of the decoupling capacitors is usually greater than the height of the connectors between the integrated circuit and the circuit board on which it is mounted, it is necessary to form a hole in the circuit board through which the decoupling capacitors can extend.
While this conventional technique does reduce the switching noise in the integrated circuit, it has several drawbacks. For instance, the hole in the circuit board allows the integrated circuit to flex under pressure from the heat sink/spreader, which reduces the thermal contact between the integrated circuit and the heat sink/spreader. Further, the even distribution of the decoupling capacitors across the integrated circuit is not optimal for reduction of switching noise.